Industrial wastewater and household wastewater often contain an oil component. For example, oil-containing wastewater is discharged from various kinds of equipment at oil refineries. Vegetable oil manufacturing plants also discharge wastewater containing oil and fat in the course of producing soy bean oil, canola oil, corn oil and the like. Moreover, water-soluble cutting oil (mineral oil) is used to cool and lubricate cut surfaces at automobile manufacturing plants and many other manufacturing plants that use machine tools, and waste water containing this water-soluble mineral oil is sometimes discharged from these manufacturing plants. Wastewater containing relatively high concentrations of oil derived from animal and plant oil is also discharged by food processing plants, hotels, restaurants and the like. Consequently, the oil component needs to be removed when treating such oil-containing wastewater.
Conventionally, methods of removing the oil component from oil-containing wastewater have including methods in which the oil component is removed by adsorption using an adsorbent, and known adsorbents include porous materials such as activated carbon and activated coke (see for example Japanese Patent Application Laid-open No. 2002-254072).